A touch sensor has been known as an interface for a user to input information to a display device. When the touch sensor is installed to overlap a screen of the display device, the user can operate an input button, an icon, and the like displayed on the screen, and can easily input information to the display device.
In recent years, the demand for a so-called hover sensing (non-contact sensing) technique for detecting coordinates projected onto a display screen of a detection target such as a person's finger not contacting the display screen and spaced apart therefrom and a user operating an input button, an icon, or the like displayed on the display screen has increased.
For example, Japanese Laid-Open Patent Publication No. 2013-125536 (Japanese Patent Application No. 2012-75731) discloses a touch panel including a lower transparent substrate having concave portions and convex portions continuously formed therein, a lower detection electrode formed on the lower transparent substrate and formed in one direction to be continuous to the concave portions and the convex portions, an upper transparent substrate having convex portions and concave portions alternating with the the concave portions and the convex portions of the lower transparent substrate, and an upper detection electrode formed on the upper transparent substrate and formed in one direction having the convex portions of the upper transparent substrate respectively corresponding to the concave portions formed in the lower detection electrode.
In the hover sensing, a capacitance between a touch electrode on a display surface and a finger spaced approximately several centimeters apart therefrom is detected. However, in this case, the difficulty of efficiently forming an electric field up to the finger spaced approximately several centimeters apart from a touch sensor makes the hover sensing difficult.